Methods of the nTRACER Direct Whole Core Transport Code and Validation through BEAVRS MIT PWR Benchmarks
nTRACER is a direct whole core transport code being developed at Seoul National University for practical applications to pressurized water reactors and fast reactors. It employs unique calculation methods that make it possible to perform direct whole core calculations for power reactors on a LINUX cluster mounting hundreds of computing cores without any advance generation of homogenized multigroup cross sections.
The primary methods include:
- the planar MOC based 3D CMFD formulation employing SP3 axial nodal kernel,
- the subgroup formulation for direct geometry, composition, and temperature dependent resonance shielded cross section generation,
- Krylov subspace method based subpin level depletion calculation for effective evaluation of matrix exponentials,
- subchannel thermo-fluid and intra-pellet heat conduction calculation for incorporation of the thermal feedback effects considering cross flow and fuel temperature profiles, and
- efficient transient calculation employing the conditional MOC update within the framework of the transient CMFD calculation.
Supplementary methods such as quadratic depletion with precorrection for efficient Gadolinium depletion and control rod decusping considering intrapellet flux profiles are also implemented. The code can perform a cycle depletion calculation with a single input deck without any prior calculation step to generate subpin level power, temperature, and isotopic inventory distributions at each burnup step. Restart calculations are possible for reload cycle calculations and transient calculations at a specific burnup step. The accuracy of the code was validated by a series of core follow calculations for two OPR1000 reactors of Korea and also for the MIT BEAVRS real PWR core benchmark for which measured data such as critical boron concentrations, control rod worths, and instrument reactions rates are available. The seminar will cover the primary methods and performance of the nTRACER code.